Reflector



July 34, 1925.

s. E. BROWN REFLECTOR Original Fild May 16. 1918 Patented July 14, 1925.

scum a snow, or DEDHAM, MASSACHUSETTS.

REFLECTOR.

Application filed May 16,1918, SerialNo. 234,992. Renewed June 16, 1919.Serial No. 804,737.

To all whom. it may concern:

Be it known that I, SUMNER E. BROWN, a citizen of the United States,residing at Dedham, in the county of Norfolk and State of Massachusetts,have invented new and useful Improvements in Reflectors, of which thefollowing is aspeciiication.

This invention relates to reflectors for lamps and is particularlyintended to be used in connection with headlights of mo tor cars. Underthe'term lamp as used in the preceding statement I include all sourcesof illumination, whether the same be an electric are, an incandescentfilament, a flame, or any other means which may be availed of to producelight. And in 'describing the invention as particularly adapted for theheadlights of motor cars,

I do not intend 'to' imply any restriction as to the field or scope ofits use, but on the contrary I intend to protect the invention asapplied to a reflector used in any connection where the reflection oflight in a relatively concentrated beam is desirable.

The main object of the invention is to embody in the construction of thereflector means for securing a certain predetermined spread of light inone plane while maintaining a suflicient concentration of light in theplane at right angles thereto. More particularly, as applied to aheadlight reflector .for automobiles and other traveling vehicles, myobjeet is to secure a given horizontal spread of light, whereby toilluminate sufliciently objects at the sides of the highway or road andavoid concentration of all of the reflected rays in a narrow beam of toogreat intensity; and to accomplish this result without at the same timecausing an unnecessarily great vertical spread of reflected light, andparticularly without throwing reflected rays upwardly.

The invention consists essentially in forming the reflector in a numberof different reflecting surfaces or panels, which for convenience ofthis description I will call zones I so arranged with respect to thesource of light as to reflect rays with the desired lateral spread, andare otherwise so formed as to effect the desired concentration in theplane at right angles to that in which such spread occurs,

In the drawings wherein I have illustrated the invention, Figure 1represents partly in plan and partly in horizontal section an embodimentof my invention in a position adapting it tothe uses of an autoelevation of the reflectoras viewed froma direction approximately at anangle of to the vertical median plane.

In order most clearly and concisely to explain the principles of theinvention, I will describe'the embodiment thereof in a reflectordesigned for automobile headlights to secure horizontal spread of lightwithout vertical spread; and in connection therewith 'will explain thereason for and the utility of the invention.

. In the development of headlight reflectors for automobiles, attentionhas been first di .rected to securing concentration of the reflectedrays so as to give bright illumination to the roadin front of the car,and next to the elimination of high rays so as to avoid dazzling theeyes of drivers approaching the light. While these effects have beenefficiently accomplished, their accomplishment has been accompanied withthe result of so narrowing the field of illumination and so brilliantlyilluminating the road in front of the light as to intensify ,thedarkness outside of the illuminated field, and this has given rise tothe danger that the driver of the car, whose eye has become accustomedto the bri ht illumination in front and thereby ma e less receptive tofeeble light rays coming from outside the illuminated field, will notperceive persons about to step heedlessly in front of the car, and hasactually been the cause of many accidents. In the effort to avoidaccidents from this cause, various devices for diffusing the light havebeen produced, but so far as I vamaware such devices have also resultedin loss of efliciency in the projection of the desired illuminatingrays, and have not confined the dispersion to the horizontal plane,which alone'is necessary, but have diffused light in all directions,which is objectionable.

Ihave accomplished the desired result of spreading the light laterallywithout at the same time unavoidably spreading it vertically or emittingbrilliant high rays, and without loss of efliciency, by making thereflecting surface in a plurality of panels or zones, which aresegmental, substantially cylindrical, concave surfaces, and of which theinclination of their elements with re spect to the rays of lightemanating from the lamp, and their respective widths are of the requiredvalues to cause such lateral spread as is required for a given case.Referring to Figure 1 it will be seen that the reflector is symmetricalon both sides of a vertical central plane, and that on one side of saidplane it is formed with zones A, B, and C, and on the other side of theplane with zones A, B, and C. Such zones are segments of cylindricalsurfaces, by which I mean that they are segment-s of curved surfaceseach of which is generated by a moving straight line which continuallytouches a given curve, and in all of its positions is parallel to agiven straight line not in the plane of the curve. The elements of eachsurface so generated correspond to different positions of the generatingline, and all such elements are parallel to one another. That part ofFigure 1 which is in section shows the elements of the zones in thehorizontal medial lane of the reflector, that is, the horizonta planewhich passes through the lamp or point of illumination. The cylindricalsurface thus defined need not be the surface of a right cylinder, butmay fit the outline of a curve of any form; and the bounding edges ofthe zones need not be perpendicular to the elements of such surfaces,but must actually be variously inclined to such elements, as shown inthat part of Figure 1 which represents a plan view, in order that thezones maybe matched together.

The widths of the several zones and the angles which their elements makewith the vertical median plane may have many values, and aredeterminable in accordance wit-h the limit of size of the reflector andthe width of light spread desired. The practical'limiting factors to thesize of the reflector are the permissible diameter of the headlightcasing and the distance which must intervene between the lamp and thenearest point of the reflector. The position of the lamp or other lightsource is indicated at L in Figure 1.

In the embodiment chosen for illustration it has been assumed that thehorizontal spread of the reflected light desired is 45, that is 22 toeach side of the vertical medial plane. Therefore the zones have beenlaid out of such width and with their surface elements horizontal and atsuch inclinations to the Vertical plane that the rays from the lampreflected from the opposite edges of each zone will be reflected withthis degree of spread. Referring for example to the'zone B of Figure 1,the line 6 indicates the ray from the lamp which strikes the edge ofzone B nearest to the central plane. This ray is reflected along theline b 22 degrees to the left of the axis. The ray b from the lampstriking the outer edge of the zone B is reflected along the line b 22to the right of the axis. The rays which are reflected from the adjacentedges of the zones A and A are reflected on diverging lines a and awhich make the angles above indicated with the vertical medial plane andare consequently parallel to the rays 6 and b, respectively, it beingunderstood, however, that the reflected ray a is reflected from the zoneA and that the ray a is reflected from the zone A. The ray a from thelamp striking the remoter edge of the zone A is. reflected on the line aparallel to the reflected rays (1 and b. In like manner the rayindicated at c which strikes the nearest edge of the outermost zone C isreflected on the line 0 parallel to b and a. The opposite limitingreflected ray from the zone C is not shown because the limiting outerdimension of the reflector forbids this zone being carried out to thepoint where a ray from the lamp would be reflected at so large an angleas 22 The linesa b and 0 rep-resent the light rays, which, striking theseveral zones, are reflected straight ahead, and the reflectionsthereofl are shown at a, b and 0, respectively. It will be understoodthat the rays striking the zones A, B, and C are reflected in anequivalent manner but in the reverse order to that described. All thereflected rays, that is the rays reflected from all of the severalzones, are within the limits of spread of the beam of rays'hereinbeforedescribed. Thus each zone reflects rays in a fan, and such raysreflected from different zones occupy in part the same field. To thespreading fan of light composed of the reflected rays is added the lightof direct rays issuing from the lamp, all of which gives suflicientlight to make visible objects and persons at the sides of the road ashort distance ahead of the car, enabling the driver to see them in timeto avoid accidents. This efl'ect is secured without undue spread oflight, without loss of efiiciency,

and without diminishing the concentration of light in the center of theilluminated field below the degree necessary for making the road aheadclearly and easily visible.

Evidently the result accomplished as de scribed depends upon the law ofoptics that the angle of reflection of light is equal to the angle ofincidence of the ray upon the reflecting surface. Therefore by arrangingthe elements of the reflecting zones at the IUD proper angles to therays which impinge on them from the lamp, and making the zones of theproper width in accordance with this law, a spread of light of anydesired angle, either greater or less than that herein shown anddescribed for illustration, may be obtained.

The best and most exact results according to the principles of thisinvention are produced when the reflecting zones are true cylindricalsurfaces, that is when the elements thereof are straight lines, butapproxi-' shown a form of curvature which may be given to each of thezones, and is effective to reflect the lower rays straight ahead and toreflect the upper rays from the lampdownwardly in order to illuminatethe road far ahead and eliminate high rays which would have a tendencyto dazzle drivers of approaching cars. In this figure the curved line Arepresents a vertical section of the zone A, and correspondingly A, on aplane perpendicular to the elements of these zones. The curve Brepresents a section similarly determined of the zones B and B, while Crepresents the same character of section of the zones C and C. Byreference to the curve A and the rays which are shown as emanating fromthe lamp L and reflected from the curve, it will be recognized that thelower part of the curve is a parabola, arranged to reflect rayshorizontally, and the upper part is elliptical arranged to reflect raysconvergently downward. The curves I and C are similar in principle butof different focal length, by reason of the fact that their elements areat different distances from the lamp than the zone A. Figure 1illustrates these differences; showing by the broken line f theperpendicular distance from the lamp to the nearest point of the zone A,which is the focal length of the curve A the broken line f showing theperpeiulicular distance from the lam to the extension of the nearestelement 0 the zone Ii. and being the focal length of this zone; while 7'is the corresponding distance from the lamp to the prolongation of thenearest element of zone C to the lamp, and is the focal length of thiszone. Of course as the zones are cylindrical, the intersections ofPilt'll surface with all planes perpendicular to its elements have thesame curvature.

Inasmuch as the zones,-being cylindrical, have straight lines as theirelements, their foci are straight lines and not points. The focal lineas to any zone is the locus of the focal points of all sections of thecylindrical surface cut by planes perpendicular to its elements. In.another mode of statement such focal line is parallel to the elements ofthecylindrical surface and passes through the focus of the curve locatedby the intersection with the cylindrical surface of any planeperpendicular to its elements. The previously described location andarrangement of the different zones cause all of their focal lines tointersect at a common point, and at this point the light source islocated.

A general'statement of the salient characteristics of reflectorsembodying the invention may be made as follows Having regard to themedial plane of the reflector perpendicular to the direction of thedesired spread of light, which may be called for the purposes of thisstatement a reference plane, the total reflecting surface is composed ofa plurality of concave zones on each side of the reference plane, eachof such zones having a cylindrical focalizing surface, and the severalzones being of different focal lengths and being located at suchdistances from the reference plane and at such angles to said plane thattheir focal lines intersect at a common point. When the.

parts of the reflecting surface at opposite sides, of the referenceplane are symmetrical, the common point of all the focal lines is inthat reference plane. This intersection point may be considered as thefocus of the entire reflector. The lamp or light source is located in orso near to such focus as will cause the desired results in respect tothe reflection of light. The preferred characteristic is that thedifferent zones of the reflecting surface shall be so''- inclined to thereference plane and of such widths that'the rays reflected from all thezones will occupy substantially the same position in space. Theconsequence .of the foregoing facts is that all the surface elements ofall of the zones are in planes perpendicular to the reference plane andparallel to one another and to the spread of light, although thepositions of said elements in said planesare inclined to the referenceplane and to the elements of adjacent zones. Where adjacent zones meet,lines of lishedin planes which may be here considered'as intersectionplanes. Such ininterscction are estab-.

tel-section planes are perpendicular to the plane of light spread, andin the preferred form of the invention, are likewise parallel to oneanother. However, minor variations in one or more of these .conditionsmay be lnade within the scope of the protection which I claim herein,provided the results secured, and the means for effecting them,

are substantially as setforth in this specification.

In the particular case of a reflector arranged to secure horizontalspread of light,-

which is the case described in detail in the foregoing specification,the surface elements of the zones are horizontal and the reference planeis vertical. The boundaries or edges of the several zones or panels thusextend and lie in planes which are transverse to the previously definedhorizontal medial plane of the reflector, and intersect such horizontalplane. The scope in which I claim protection is by no means limited tothis particular case since the same reflector may be mounted inivariouspositions wherein its surface elements and reference plane have otherrelations tothe horizontal and vertical. It will be apparent from theforegoin description and analysis that a re ector formed with zones orpanels having the curvature and arrangement thus described conforms ingeneral to a concave focalizing reflector, and that the outline of thereflector in horizontal midsection so conforms, in a general orapproximate way, to a. focalizing curve, but with such divergence fromsuch' curve as follows from making the light dispersing zones;substantially straight elements.

The reflector the characteristics herezdescribedQmayreadiIy be made from.sheet meta'lbybeing formed between appropriately-shaped dies, and inthese drawings I have represented the reflector as being so made. ofsuch material. As thus made the outer surfaces have substantially thesame form and characteristics as the reflecting surfaces, but this isnot important since it is only the reflecting surfaces which must havethe essential characteristics herein pointed out, and the'outer surfacesmay have any form. The reflector, therefore, may be made otherwise thanby pressing between dies and of other material than sheet metal. It isintended to be mounted in the casing of the headlight, and, asmanufactured, is provided with any means for such purpose, and means formounting a lamp, such as are already familiar in the art.

What I claim and desire to secure by Letters Patent is:

1. A reflector having a general contour of a concave focalizing surfaceand characterized by curvature variations constituting a plurality ofpanels extending in a general direction intersecting the horizontalmedial plane of said reflector, said panels providing a series ofreflecting surfaces configurated to project from a source of lightwithin said reflector, a beam of light of greater extent horizontallythan vertically.

' 2. A projecting light reflector adapted to a point light source andconforming in horizontal and vertical axial section generally to afocalizing curve, said reflector being formed with a plurality ofsurfaces which, in vertical section, are curved similar to saidfocalizing curve, but in horizontal section depart from said curvesufficiently to spread the light in horizontal planes.

3.- A reflector having the general contour of a concavefocalizingsurface, said reflector comprising a plurality of flattenedpanels, each of said panels being adapted to reflect from a source oflight within said reflector, a beam of light of greater extenthorizontally than vertically, said panels-being positioned with respectto each other and to the light source so as to sup'erimpose the beams tooccupy the same position'in space.

4. A projecting reflector having its reflecting surface on each side ofa medial reference plane comprising a plurality of cylindrical zones,the elements of the several zones being arranged at different angles tosaid reference plane but all in planes perpendicular thereto.

5, A projecting reflector having a. plurality of cylindrical zones ofsimilar cross section, but-of different-focal lengths with noncoincidentfocal lines intersecting at a common focus.

6. A projecting reflector having a plurality of c lindrical zones ofdifferent focal lengt is having non-coincident focal lines in tersectingat a common point and all the'surface elements of said zones being inparallel planes. i

7.. A projecting reflector having a reflecting surface comprisingdistinct cylindrical zones in. which the surface elements are allhorizontal but inclined to the'elements of adjacent zones, difi'erentones of such zones being generated with respect to curves having acommon focus and respectively different focal lengths. 8. A projectingreflector having a reflectmg surface comprising distinct cylindricalzones in which the surface elements are all horizontal, differentones'of such zones being generated with respect -to parabolic curveshaving a common focus but respec tively (lifl'erent focal 'lengths'andnon-cont cident intersecting focal lines.

9. A projecting reflector having a reflecting surface comprisingdistinct cylindrical zones in which the surface elements are allhorizontal, different ones of such zones being'generated with respect tocurves ivhich above the horizontal axial plane of thereflector areelliptic and below 'said plane are parabolic; said curves havingnon-coincident focal lines intersecting at a common focus andrespectively diflerent focal lengths.

10. The combination of a project-ing reflector having a focal point anda light source located approximately at such focal point; the reflectingsurface of said reflector comprising distinct cylindrical zones allfollowing curves which have a common focus in said focal point, certainof said zones having different focal lengths and being arranged withrespect to said focal point to reflect the beams emanating from thelight source over substantially the same predetermined area.

11. In a projecting lamp the combination of a reflector having .aplurality of cylindrical zones, the elements of which are all inparallel planes, following similar curves which have noncoincidentalintersecting focal lines and respectively different focal 1'5 lengths asto certain zones, and a point light source located approximately at theintersection of said focal lines; I

In'testimony whereof I have aflixed my, signature:

SUMNER E. BROWN.

